Process for dyeing hydrophobic fibers with disperse dyes



United States Patent @fi ice 3,058,798 Patented Oct. 16, 1962 N.J., assignor Wilming- No Drawing. Filed Feb. 19, 1959, Ser. No. 794,237 1 Claim. (Cl. 8-151) This invention is directed to a novel process for dyeing hydrophobic fibers in tow form.

Hydrophobic tow fibers, such as polyethylene terephthalate tow or cellulose triacetate tow, are multifilament strand of fibers obtained directly from spinnerettes used in the manufacturing process of the artificial fiber. This bundle of fibers is used in the preparation of staple fiber which is made by cutting the tow to short fibers and then spinning the individual short fibers into the spun yarn.

Tow fiber is conventionally dyed in readily available raw stock equipment as for example that illustrated as FIG. 11 and described on pages 632 to 635 of the American Cotton Handbook, 2nd edition, Textile Book Publishers, 1949. In the conventional process, the tow is carefully packed into a perforated basket which is placed into the machine. Then a concentrated dye dispersion is added, after adding water, the liquor is circulated through the machine and forced through the tow at elevated temperatures of about 205 F. to 250 F.

One of the problems encountered with this conventional process is due to the use of disperse dyes for dyeing hydrophobic fibers. Because the tow acts as a filter during the addition of the dye dispersion and during the dyeing procedure, it removes particles of the dye from its aqueous dispersion and the resulting dyed goods are unlevel being heavier on the outside and inside layers of the tow bundle than in the center. A further disadvantage due to this filtration efiect is obtained because the dye remains essentially on the surface and the dyed fiber shows poor crock fastness.

It is, therefore, an object of the present invention to provide a novel process for the dyeing of a hydrophobic fiber in tow form. It is a further object of this invention to attain a dyed hydrophobic fiber in tow form, which fiber is dyed effectively throughout to result in a level dyeing and desired fastness properties. These and other objects will become apparent in the following description and claim.

More specifically, the present invention is directed to a process of dyeing hydrophobic fibers in tow form with disperse dyes, which process involves the improvement which consists of first padding the tow with an aqueous dispersion of the disperse dye followed by placing the padded tow into a conventional raw stock dyeing machine and circulating water through the padded tow at a temperature of 200 F. to 300 F. to thereby fix the dye on the fiber.

The general procedure followed is one wherein the tow fiber as received from the manufacturer in the form of a bundle is mechanically passed through a dye bath containing a disperse dye formulation. The tow picks up the dye dispersion and the impregnated tow is then placed in a perforated basket which is placed into a conventional raw stock dyeing machine. Then water is added to the machine in an amount suificient to enable circulation of liquid through the system. Usually the amount of water used will be ten times the weight of tow fiber in the raw stock machine. Any additives to be used in the dyeing process may also be added at this point; e.g., a small amount of acetic acid to control the pH of the dye bath. The aqueous system is then heated and circulated through the machine, the liquid being pumped from a hold tank or expansion tank to the raw stock machine proper, through the tow, out the machine and back to the expansion tank. When the proper temperature for fixing the dye on the fiber is reached, the circulation may be cut oil, if desired, and the dyeing process continued in the raw stock machine. Preferably, the circulation of water is continued throughout the dyeing operation. Dyeing is completed in about one hour at about 200 F. to 300 F. after which the contents of the machine are allowed to cool. The tow is then removed and is found to be levelly dyed.

Representative examples of the hydrophobic tow fibers useful in the process of this invention are polyester fibers such as Dacron" polyethylene terephthalate (both unmodified and acid modified), hydrophobic cellulose derivatives such as Arnel cellulose triacetate, polyacrylic fibers such as Orlon acrylic fiber, fibers which are copolymers of vinyl chloride and acrylonitrile such as Dynel polyvinyl-acrylic fiber and the like.

Conventional disperse dyes are operable according to the present invention and include as representative examples:

The yellow dye of prototype number 242. The yellow dye of prototype number 5 34.

The yellow dye of prototype number 583.

The blue dye of prototype number 619. The blue dye of prototype number 227.

The blue dye of prototype number 499.

Other useful dyes are those which are known from the literature or which are used in practice for the dyeing of aromatic polyester fibers. Thus there may be used for example acetate rayon dyestuffs, for example, the aminoanthraquinones and aminoazobenzenes and their derivatives which are actually used for the dyeing of cellulose acetate rayon or the use of which for such dyeing is described in the literature on the subject. There may also be used, for example, dyestufis which contain a diazotisable group the dyestuffs being diazotised on the fiber and the diazotised dyestuff coupled with, for example, beta-naphthol, acetoacetanilide or 2:3-hydroxynaphthoic acid, etc.

Dye mixtures may also be used to shade as desired.

The novel process of this invention will preferably be used for obtaining heavy shades and the preferred concentration of dye on the fiber will be between 5% and 15%. However, this process will also achieve light or pastel shades and in this case the amount of dye on the fiber will be as low as 0.01%

The shade of the finished dyed tow is controlled by the dye concentration of the pad bath and the pick-up used. For example, if a certain shade is desired which is normally obtained by dyeing with a dye liquor containing 10 parts of dye per 100 parts of fiber being dyed, then the pad bath of this process will contain 10 parts of dye for each 100 parts of tow padded at 100% wet pick-up. Or, if a Wet pick-up is used in padding the tow, the same effect can be achieved by using 11.1 parts of dye per parts of tow. Usually the wet pick-up used will be between 50% and 100%.

Representative examples illustrating the present invention are as follows:

Example 1 Two pounds of polyacrylom'trile fiber tow (Orlon fonate wetting agent.

polyacrylic tow fiber) was padded at 80% wet pick-up with a bath containing on a weight basis 1% of a commercial red disperse dye of prototype number 370, 0.1% sodium alginate and 0.003% of a sodium alkyl aryl sul- The padded tow was then placed in the raw stock basket in a raw stock dyeing machine and suflicient water added to permit its circulation through the equipment. 7 to obtain 0.25% acetic acid on the weight of the fiber. (Acid is used to keep the pH below 6 since higher pH values may cause decomposition of the dye.) After circulating the water at 225 F. for 1 hour, the tow was removed from the machine and found to be levelly and uniformly dyed a pink shade. No evidence of dye filtering by the tow was found.

Example 2 Following the details of Example 1, 130 parts of cellulose triacetate tow fiber (ArneP triacetate fiber) was padded with a dye bath containing 3.0% of a yellow dye of prototype number 534. The padded tow was treated as described in Example 1 and after removal from the raw stock machine, the tow was found to be levelly dyed a heavy yellow shade. No evidence of filtering was observed.

Example 3 Glacial acetic acid was added diazotization carried out in the machine at F. with a solution of 6% by weight of fiber of sodium nitrite and 12% (OWF) sulfuric acid. The tow was then rinsed, scoured in the machine and dried. An excellent level black shade was obtained.

Any of the heretofore described hydrophobic tow fibers may be substituted in the preceding examples with any of the various described dyes to achieve substantially the same results.

As many apparently widely diiferent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claim.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

In the process of dyeing hydrophobic fibers in tow form with disperse dyes, the improvement which consists of first padding said tow with an aqueous dispersion of a dispersed dye followed by placing the padded tow into a raw stock dyeing machine and circulating water through the padded tow at a temperature within the range of 200 F. to 300 F. to fix said dye on said tow fiber.

Zimmerman: Amer. Dyest. Rep., Aug. 17, 1953, pages 547-550 (esp. page 549). 

